1. Field of the Invention
The present invention relates to a lens shading correction apparatus and method in an auto focus camera module.
2. Discussion of the Related Art
A camera module is mounted on products having various camera functions such as a portable terminal, a notebook computer, and a PDA (personal digital assistant), and to date the capacity of camera modules has so improved to as to be compared to a generally used digital camera.
Generally, an image photographed by an image photographing device has several kinds of information on a processing object corresponding to a subject, but a case frequently occurs that components of a luminance signal and a color signal corresponding to that image signal are concentrated and distorted owing to processing objects, performance of an imaging device or imaging conditions. Therefore, a camera module experiences compensations such as a lens shading correction, an auto exposure and an auto white and then proceeds on a capture of an image. A surrounding area of an image sensor in such a camera module does not receive sufficient light due to optic characteristics of a lens, and as a result of this attenuation of a signal is caused, which is called a lens shading. An attenuation of signals resulting from a lens shading varies from a position of pixels and colors. Therefore, an image signal processor (ISP) corrects an attenuation of signals in a surrounding area through an image processing procedure called a lens shading correction in a peripheral area to obtain a more improved image.
Same fixed lens shading correction is applied with mass-produced camera modules. A gain table for applying a lens shading correction is batchedly generated to be stored in a memory, and an image signal processor by using a gain table stored in the memory corrects a gain per each pixel to compensate a lens distortion. However, a camera module having an auto focus function has a problem in that a distortion variation of a lens shading compensation can occur while a lens is moving to focus on a subject.